Originally published on DebugRadar.
Meta Description (148 chars): SQL Server slowing down after the October 2026 update? Linked-server connections stay open and pile up. Close idle sessions and get the mitigation.
Quick Fix Summary
- Problem: After Windows updates released October 13, 2026 and later, connections created by SQL Server linked-server queries can stay open after the queries finish — and they pile up, slowing the server down over time.
- Fix: No patch yet. Microsoft promises an out-of-band Windows update "in the next few days" (no date), with an interim mitigation available only through Microsoft Support for Business.
- Relief now: Manually close idle connections left open by the bug, or restart the SQL Server service to restore stability — both are temporary, and the problem returns as new queries run.
Technical Root Cause
| Error Code | Affected Version | Root Cause | Current Status |
|---|---|---|---|
| No error code — linked-server connections remain open after queries complete | SQL Server linked-server queries using OLE DB providers to external databases (Oracle and PostgreSQL named as affected); Windows 10/11 and Windows Server 2012 and later, except Windows 11 26H2 | Change in the October 2026 cumulative updates (including KB5126646 / KB5127648) stops the OLE DB provider interface from releasing connections after linked-server queries finish | Still broken as of Nov 14, 2026 — out-of-band fix promised "in the next few days", no date; mitigation via Microsoft Support for Business only |
Step-by-Step: Deal With the SQL Server Connection Leak
Step 1 — Confirm This Is the Bug
Check whether the slowdown started after the October 13, 2026 Windows updates. Then look for external connections that stay open after their queries finish. A diagnostic query against sys.dm_exec_connections shows live connections; if connections to linked servers (Oracle, PostgreSQL) keep growing long after the queries that opened them are done, this is the bug. (Diagnostic tip from third-party coverage, not Microsoft guidance.)
SELECT session_id, connect_time, net_transport, client_net_address
FROM sys.dm_exec_connections
WHERE net_transport = 'TCP'
ORDER BY connect_time;Step 2 — Close Idle Connections to Relieve the Load
Manually close the idle connections the bug left open. This frees resources right away — but it is temporary. Every new linked-server query can leave another connection behind, so the pile-up starts again. Treat this as first aid, not a fix, and do it during a quiet window where you can see what is idle and what is still running.
Step 3 — Restart the SQL Server Service If Performance Has Degraded
If the server is already slow, restarting the SQL Server service clears every leaked connection and restores normal speed. Plan the restart: it interrupts active queries and transactions, so warn users first and pick a maintenance window. After the restart, the leak resumes with the next linked-server queries — expect to repeat this until the patch lands.
Step 4 — Get the Interim Mitigation From Microsoft Support for Business
Microsoft's only published path to a real mitigation before the patch is Microsoft Support for Business. Open a case and reference the linked-server connection issue from the October 2026 updates. Have ready: your Windows update KB numbers, the SQL Server version, and the OLE DB providers in use (Oracle, PostgreSQL, or others).
Step 5 — Watch for the Out-of-Band Fix
Microsoft says the fix will arrive as an out-of-band Windows update "in the next few days". Check Windows Update and Microsoft's release health dashboard — do not assume a normal Patch Tuesday will carry it. This is the same update train that broke Windows activation in November — see our Fix: slmgr.vbs 0x80041008 Invalid Parameter — and the same November update that broke Sage 50: Fix: Sage 50 Crashes After KB5132061 Update.
If you run SQL Server across a fleet, stop firefighting server by server: This bug hits hardest when you are restarting services and chasing leaked connections on machine after machine. ManageEngine Endpoint Central manages patching, configuration, and server health from one console, so one bad update does not turn into a week of manual restarts. (Affiliate link — DebugRadar earns a commission if you sign up through it.)
FAQ
Is my SQL Server data at risk?
No data loss has been reported. The bug leaks connections and degrades performance over time — it does not corrupt databases. The risk is a slow or unresponsive server, not lost data.
Will restarting the service fix it for good?
No. A restart clears the leaked connections, but the next linked-server queries leak new ones. Only Microsoft's out-of-band fix ends the cycle.
Which linked servers are affected?
Microsoft names Oracle and PostgreSQL as known-affected OLE DB providers. Any linked-server query using an OLE DB provider to an external database can hit it.
Sources: BleepingComputer, November 12–13, 2026; The Register, November 12, 2026; Neowin, November 12, 2026; Microsoft Windows release health dashboard (issue opened November 11, 2026).
Read the full guide on DebugRadar: Fix: SQL Server Connections Stay Open After Update
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